Light emitting device

ABSTRACT

A light-emitting structure includes a transparent substrate; a first transparent conductive layer formed on the transparent substrate and having a first top surface and a second top surface substantially coplanar with the first top surface; a first light-emitting stack formed on the first top surface; and a first electrode directly formed on the second top surface.

RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 13/730,130, entitled “LIGHT EMITTING DIODE HAVING ATRANSPARENT SUBSTRATE”, filed Dec. 28, 2012, which is a divisionalapplication of U.S. patent application Ser. No. 13/114,384, entitled“LIGHT EMITTING DIODE HAVING A TRANSPARENT SUBSTRATE”, filed May 24,2011, which is a continuation application of U.S. patent applicationSer. No. 11/724,310, entitled “LIGHT EMITTING DIODE HAVING A TRANSPARENTSUBSTRATE”, filed Mar. 15, 2007 claiming the right of priority based onTaiwan application Ser. No. 090115871, filed Jun. 27, 2001; the contentof which is incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a light-emitting device, morespecifically to a light-emitting device with a light-emitting stack on atransparent conductive layer.

DESCRIPTION OF BACKGROUND ART

Light emitting diodes (LEDs) are employed in a wide variety ofapplications including optical display devices, traffic lights, datastorage equipment, communication devices, illumination apparatuses, andmedical treatment equipment. Some of the main goals of engineers whodesign LEDs are to increase the brightness of the light emitted fromLEDs and to reduce the cost of manufacturing LEDs.

U.S. Pat. No. 5,783,477 discloses a method of bonding two compoundsemiconductor surfaces to produce an ohmic contact interface. The methodof manufacturing a prior art LED is to create an ohmic contact interfaceby aligning the crystallographic orientation and rotational alignment oftwo semiconductor surfaces and applying uniaxial pressure to thesemiconductor wafers at a temperature of 1000° C. In actual procedure,however, it is difficult and expensive to align the crystallographicorientation and rotational alignment of the two semiconductor surfaces.

SUMMARY OF THE DISCLOSURE

A light-emitting structure includes a transparent substrate; a firsttransparent conductive layer formed on the transparent substrate andhaving a first top surface and a second top surface substantiallycoplanar with the first top surface; a first light-emitting stack formedon the first top surface; and a first electrode directly formed on thesecond top surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a high brightness light emittingdiode having a transparent substrate according to the first embodimentof the present invention.

FIG. 2 is a cross sectional view showing a first semiconductormultilayer before wafer bonding during the manufacturing methodaccording to the present invention.

FIG. 3 is a cross sectional view showing an amorphous interface layerand a second semiconductor multilayer before wafer bonding during themanufacturing method according the present invention.

FIG. 4 is a cross sectional view showing a third semiconductormultilayer after wafer bonding, but before removal of thenon-transparent substrate during the manufacturing method according thepresent invention.

FIG. 5 is a cross sectional view showing a third semiconductormultilayer after removal of the non-transparent substrate and formationof an ITO transparent conductive layer during the manufacturing methodaccording the present invention.

FIG. 6 is a cross sectional view of a high brightness light emittingdiode having a transparent substrate according to the second embodimentof the invention.

FIG. 7 is a cross sectional view of a high brightness light emittingdiode having a transparent substrate according to the third embodimentof the invention.

FIG. 8 is a cross sectional view of a high brightness light emittingdiode having a transparent substrate according to the fourth embodimentof the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 is a cross sectional view of a high brightness light emittingdiode (LED) 1 having a transparent substrate according to the firstembodiment of the present invention. In the LED 1, an indium tin oxide(ITO) amorphous interface layer 11 is formed on a sapphire transparentsubstrate 10. A top surface of the ITO amorphous interface layer 11comprises a first surface region and a second surface region. The LEDfurther comprises layers stacked upon each other on the first surfaceregion in the following order, bottom to top: a contact layer of p+-typeGaAs 12, a cladding layer of a p-type AlGaInP 13, a multiple quantumwell (MQW) light-emitting layer 14, a cladding layer of n-type AlGaInP15, a stop layer of n-type AlGaAs 16, and an ITO transparent conductivelayer 18. A first electrode 19 is located on the ITO transparentconductive layer 18, and a second electrode 20 is located on the secondsurface region.

FIG. 2 and FIG. 3 illustrate a method for manufacturing the lightemitting diode 1 according to the first embodiment of the presentinvention. A first semiconductor multilayer 2 is created by firstforming an n-type stop layer 16 of AlGaAs on an n-type GaAssemiconductor substrate 17. Then an n-type cladding layer 15 of AlGaInPis formed on the n-type stop layer 16. An MQW light-emitting layer 14 ofAlGaInP is formed on the n-type cladding layer 15. A p-type claddinglayer 13 of AlGaInP is formed on the MQW light-emitting layer 14, and ap+-type contact layer 12 of GaAs is formed on the p-type cladding layer13. Next, a second semiconductor multilayer 3 is created. The secondsemiconductor multilayer 3 comprises an amorphous interface layer 11 ofITO formed on a sapphire substrate 10. As is shown in FIG. 4, a thirdsemiconductor multilayer 4 is produced by inverting the firstsemiconductor multilayer 2, placing it on the semiconductor multilayer3, and bonding the first semiconductor multilayer 2 to the secondsemiconductor multilayer 3 by elevating temperature and applyinguniaxial pressure to the semiconductor multilayers. FIG. 4 and FIG. 5show the next step, which comprises the removal of the n-type GaAssemiconductor substrate 17 from the multilayer 4 and the formation of afirst ITO transparent conductive layer 18 on the n-type stop layer 16,producing a fourth semiconductor multilayer 5. Next, an interfaceexposed region is formed by etching away a portion of the fourthsemiconductor multilayer 5 from the first ITO transparent conductivelayer 18 to the ITO amorphous interface layer 11. Finally, a firstcontact electrode 19 and a second contact electrode 20 are formed on thefirst ITO transparent conductive layer 18 and the interface exposedregion, respectively.

FIG. 6 illustrates a light emitting diode 6 having a transparentsubstrate according to a second preferred embodiment of the presentinvention. A transparent substrate 611 of p-type GaP is formed on anohmic contact electrode 610. A first p+-type contact layer 612 of GaAsis formed on the transparent substrate 611. An indium tin oxide (ITO)amorphous interface layer 613 is formed on the first p+-type contactlayer 612. A second p+-type contact layer 614 of GaAs is formed on theITO amorphous interface layer 613. A p-type cladding layer 615 ofAlGaInP is formed on the second p+-type contact layer 614. A multiplequantum well (MQW) light-emitting layer 616 of AlGaInP is formed on thep-type cladding layer 615. An n-type cladding layer 617 of AlGaInP isformed on the MQW light-emitting layer 616. An n-type stop layer 618 ofAlGaAs is formed on the n-type cladding layer 617. An ITO transparentconductive layer 619 is formed on the n-type stop layer 618. Anelectrode 620 is formed on the ITO transparent conductive layer 619.

FIG. 7 illustrates a light emitting diode 7 having a transparentsubstrate according to a third preferred embodiment of the presentinvention. A transparent substrate 711 of n-type GaP is formed on afirst electrode 710. An indium tin oxide (ITO) amorphous interface layer713 is formed on the transparent substrate 711. An n-type contact layer714 of GaP is formed on the ITO amorphous interface layer 713. An n-typecladding layer 715 of AlGaInP is formed on the n-type contact layer 714.A multiple quantum well (MQW) light-emitting layer 716 of AlGaInP isformed on the n-type cladding layer 715. A p-type cladding layer 717 ofAlGaInP is formed on the MQW light-emitting layer 716. A p-type bufferlayer 718 of AlGaAs is formed on the p-type cladding layer 717. Ap+-type contact layer 719 of GaAs is formed on the p-type buffer layer.An ITO transparent conductive layer 720 is formed on the p+-type contactlayer 719. A second electrode 721 is formed on the ITO transparentconductive layer 720.

FIG. 8 illustrates a light emitting diode 8 having a transparentsubstrate according to a fourth preferred embodiment of the presentinvention. An indium tin oxide (ITO) amorphous interface layer 811 isformed on a transparent substrate 810 of glass. A top surface of the ITOamorphous interface layer 811 comprises a first surface region and asecond surface region. An n+-type reverse tunneling contact layer 814 ofInGaN is formed on the first surface region. A p-type cladding layer 815of GaN is formed on the n+-type reverse tunneling contact layer 814. Amultiple quantum well (MQW) light-emitting layer 816 of InGaN is formedon the p-type cladding layer 815. An n-type cladding layer 817 of GaN isformed on the MQW light-emitting layer 816. A first Ti-Al contactelectrode is formed on the n-type cladding layer 817. A second electrode820 is formed on the second surface region.

According to the description of these embodiments, LEDs having atransparent substrate can be manufactured by a method of bonding twochips using an amorphous interface layer. LEDs made according to thepresent invention are easier to manufacture, less expensive tomanufacture, and brighter than those made according to the prior art.

While the invention has been disclosed and described with reference tothese preferred embodiments, the scope of the invention is not limitedto these preferred embodiments. Any variation and modifications of theinvention still falls within the spirit and scope of the invention. Forexample, using a transparent conductive layer of adhesive agent insteadof a single-crystal interface layer or using a single quantum welllight-emitting layer instead of a multiple quantum well light-emittinglayer cannot escape the scope and spirit of the invention. Moreover, themanufacturing method of the present invention is also suitable formanufacturing a light emitting diode having a non-transparent substrate.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device may be made while retainingthe teachings of the invention.

Accordingly, the above disclosure should be construed as limited only bythe metes and bounds of the appended claims.

What is claimed is:
 1. A light-emitting structure, comprising: atransparent substrate: a first transparent conductive layer formed onthe transparent substrate and having a first top surface and a secondtop surface substantially coplanar with the first top surface; a firstlight-emitting stack formed on the first top surface; and a firstelectrode directly formed on the second top surface.
 2. Thelight-emitting structure of claim 1, further comprising a secondtransparent conductive layer electrically connected to thelight-emitting stack.
 3. The light-emitting structure of claim 2,wherein the first transparent conductive layer and the secondtransparent conductive layer comprises a same material.
 4. Thelight-emitting structure of claim 2, further comprising a secondelectrode formed on the second transparent conductive layer.
 5. Thelight-emitting structure of claim 2, wherein the first light-emittingstack comprises a semiconductor layer with a width equal to that of thesecond transparent conductive layer.
 6. The light-emitting structure ofclaim 2, wherein the first transparent conductive layer, the secondtransparent conductive layer or both comprise ITO.
 7. The light-emittingstructure of claim 1, further comprising a second light-emitting stackformed on the first transparent conductive layer.
 8. The light-emittingstructure of claim 1, wherein the first transparent conductive layer isa non-semiconductor layer.
 9. The light-emitting structure of claim 1,wherein the transparent substrate comprises sapphire, GaP or glass. 10.The light-emitting structure of claim 1, wherein the firstlight-emitting stack comprises a semiconductor layer with a width lessthan that of the first transparent conductive layer.
 11. Thelight-emitting structure of claim 1, wherein the first transparentconductive layer is an amorphous layer.
 12. The light-emitting structureof claim 1, wherein the first top surface and the second top surface areflat.
 13. The light-emitting structure of claim 1, wherein the firsttransparent conductive layer is a non-epitaxial layer.